Solvent Engineering Improves Efficiency of Lead-Free Tin-Based Hybrid Perovskite Solar Cells beyond 9%

Here, we report on the effect of different antisolvent dripping on film morphology and charge recombination of mixed formamidinium methylammonium tin iodide (FA(0.75)MA(0.25)SnI(3)) as a light absorber in perovskite solar cells. N,N-dimethyl methanamide (DMF) and dimethyl sulfoxide (DMSO) were used as the mixed solvent in the perovskite precursors together with tin fluoride (SnF2) as an additive. Diethyl ether (DE), toluene (TL), and chlorobenzene (CB) were employed as antisolvents for comparison. Our results show that CB as an antisolvent leads to a dense and uniform Sn-based perovskite film. The maximum power conversion efficiency of our Sn-based perovskite solar cell achieves 9.06% (9.02%) under forward (reverse) voltage scan under AM 1.5G 100 mW/cm(2) illumination. The encapsulated cells show good long-term stability with similar to 75% of their initial efficiency retained over a period of 30 days of storage. Our work suggests the promising potential to further improve the performance of Pb-free Sn-based perovskite solar cells.